Abstract: We use the Mellin-Barnes representation in order to improve the theoreticalestimate of mass corrections to the width of light pseudoscalar meson decaysinto a lepton pair, $P\to l^{+}l^{-}$ . The full resummation of the terms$M^{2}-\Lambda^{2} ^{n},$ $m^{2}-M^{2} ^{n}$and $m^{2}-\Lambda^{2} ^{n}$to the decay amplitude is performed, where $m$ is the lepton mass, $M$ is themeson mass and $\Lambda\approx m { ho}$ is the characteristic scale of the$P\to \gamma^{\ast}\gamma^{\ast}$ form factor. The total effect of masscorrections is quite important for $\eta\eta^{\prime}$ decays. We alsocomment on the estimation of the hadronic light-by-light scatteringcontribution to the muon anomalous magnetic moment in the chiral perturbationtheory.